N -(diethylthiocarbamoyl)benzimidoyl chloride reacts with methyl esters of glycine, L-alanine, L-valine under formation of pro-ligands 1 which undergo de-esterification in reactions with Cu(CH 3 COO) 2 and finally form complexes 2 with the compositions of [Cu(L-gly) 4 ] ( 2a ), [Cu(L-ala) ∞ ] ( 2b ) and [Cu(L-val) ∞ ] ( 2c ). In all complexes, Cu(II) ion is coordinated by a dianion via its (O,N,S) donor set and a bridging carboxylate O atom, and thus, adopts a distorted square-planar coordination sphere. Treatment of complexes 2 with equimolar amounts of o -phenanthroline results in the formation of square pyramidal ternary complexes with the compositions of [Cu(L)phen] (L = L-gly, L-ala, L-val) ( 3 ). Antiproliferative effects of the compounds on MCF-7 and Hep-G2 cancer cells were studied. Generally, the ternary complexes 3 are more active than the complexes 2 and the pro-ligands 1 . In each series of compounds, the derivatives of L-valine show higher cytotoxicity than those of L-alanine and glycine.